Recording & playback settings
Open your Profile Menu, then Settings → Recording & Playback.
How recording starts
By default you can press and hold the mic button to record, and release to send. If that has been producing accidental recordings for you, single-tap recording can be turned off here.
Raise to your ear
Turn this on and bringing your phone to your ear starts playing the unread messages in the conversation, the way answering a call does. Playback pauses when you lower the phone and picks up again when you raise it.
It's the easiest way to listen privately when you don't have headphones.
Playback speed
Speed is set per playback rather than in settings. See Playback speed.